fix: remove trailing CR before processing the line

lib/src/client/streamable_https.dart

@@ -378,7 +378,10 @@ class StreamableHttpClientTransport implements Transport {
         // Process the buffer line by line
         while (buffer.contains('\n')) {
           final index = buffer.indexOf('\n');
-          final line = buffer.substring(0, index);
+          var line = buffer.substring(0, index);
+          if (line.endsWith('\r')) {
+            line = line.substring(0, line.length - 1);
+          }
           buffer = buffer.substring(index + 1);
 
           if (line.isEmpty) {

test/client/streamable_https_test.dart

@@ -476,5 +476,65 @@ void main() {
       // server received and processed our DELETE request
       expect(true, isTrue);
     });
+
+    test('handles CRLF line endings in SSE events', () async {
+      transport = StreamableHttpClientTransport(serverUrl);
+
+      final messageCompleter = Completer<JsonRpcMessage>();
+      transport.onmessage = (message) {
+        print('Transport received message: ${jsonEncode(message.toJson())}');
+        messageCompleter.complete(message);
+      };
+
+      transport.onerror = (error) {
+        print('Transport error: $error');
+      };
+
+      await transport.start();
+
+      final notification = JsonRpcInitializedNotification();
+      await transport.send(notification);
+
+      await Future.delayed(Duration(milliseconds: 1000));
+
+      if (currentSseConnections.isEmpty) {
+        fail('No SSE connections established');
+      }
+
+      print(
+          'About to send SSE event, active connections: ${currentSseConnections.length}');
+
+      for (final connection in List<HttpResponse>.from(currentSseConnections)) {
+        try {
+          final message = {
+            'jsonrpc': '2.0',
+            'method': 'notifications/initialized',
+          };
+
+          final data = jsonEncode(message);
+          print('Sending SSE event with data: $data');
+
+          connection.write('event: message\r\n\r\n');
+          connection.write('data: $data\r\n\r\n');
+          await connection.flush();
+          print('Sent SSE event');
+        } catch (e) {
+          print('Error sending SSE event: $e');
+          fail('Failed to send SSE event: $e');
+        }
+      }
+
+      final message = await messageCompleter.future.timeout(
+        Duration(seconds: 5),
+        onTimeout: () {
+          print('*** TIMEOUT: No message received via SSE after 5 seconds');
+          throw TimeoutException('No message received via SSE');
+        },
+      );
+
+      expect(message, isA<JsonRpcNotification>());
+      expect((message as JsonRpcNotification).method,
+          equals('notifications/initialized'));
+    }, timeout: Timeout(Duration(seconds: 10)));
   });
 }